The build should have tried to link to /lib/libdevmapper.so, but it did not. This library is provided by sys-fs/lvm2, which is in the DEPEND list for =sys-fs/cryptsetup-1.1.3-r3. What is the output of emerge --info ; emerge --pretend --verbose sys-fs/lvm2?

I have =sys-fs/lvm2[-static] and I was able to install =sys-fs/cryptsetup-1.1.3-r3[dynamic]. I cannot tell from the output provided why this makes a difference, but I suggest rebuilding with the same USE flags I used. If that works, then file a bug that your original combination did not work.